Writing machines with fluid drive means

ABSTRACT

A writing machine of the kind in which successive writing of characters side by side and line by line is effected on a record carrier led over a platen by means of character carrying type bars arranged side by side on an arcuate pivot axis and adapted, when actuated, to pivot to effect recording at a common recording point, is such that there is provided in common for a plurality of type bars, a fluid drive for producing pivoting movement of a selected type bar, fluid driven drive elements, one for each type bar, a fluid control in the region of each fluid drive element for connecting the fluid drive to the fluid driven element appropriate to a selected type bar and a selector moveable into one of a number of predetermined positions in accordance with the type bar to be selected. The selector is arranged, when moved to such a position, to bring about the coupling of the fluid drive to the fluid driven drive element of the selected type bar by operation of the fluid control in the region of that element.

United States Patent Rummel 1 1 WRITING MACHINES WITH FLUID DRIVE MEANS[75| Inventor: Hermann RummeLDoerentrup,

Germany [73I Assignce; Nixdorf Computer AG, Paderborn,

Germany [22] Filed: Apr. 26, 1973 [21] Appl. No: 354,705

[311] Foreign Application Priority Data May 4, 1972 Germany 2221871 [52111.5. C1. 197/15; 1()1/93.1; 235/91 F [51] Int. Cl r. B4lj 23/20 158]Field of Search 197/15, 19, 20, 1 R; 101/93 C, 93.1; 235/91 F; 178/29[561 References Cited UNITED STATES PATENTS 897,959 9/1908 Cahill 197/151118916119 3/1914 Burbou 197/15 1,904,631 4/1933 Swanson 197/15 X1937,98 12/1933 Rugh r r r .r 197/15 X 2.118.113 10/1941) Klcinschmidt,178/29 2.979255 4/1961 Hubl 101/936 X 3,319,165 11/1965 Greene ct a1,197/15 X 3 3=12 297 9/1967 Greene 197/15 X FOREIGN PATENTS ORAPPLICATIONS 321144 9/1924 United Kingdom 197/15 1 1 Sept. 9, 1975Germany r 197/15 Germany 197/15 Sheridan [57} ABSTRACT A writing machineof the kind in which successive writing of characters side by side andline by line is effected on a record carrier led over a platen by meansof character carrying type bars arranged side by side on an arcuatepivot axis and adapted, when actuated, to pivot to effect recording at acommon recording point, is such that there is provided in common for aplurality of type bars, a fluid drive for producing pivoting movement ofa selected type bar, fluid driven drive elements, one For each type bar,a fluid control in the region of each fluid drive element for connectingthe fluid drive to the fluid driven element appropriate to a selectedtype bar and a selector moveable into one of a number of predeterminedpositions in ac cordance with the type bar to be selected The selectoris arranged, when moved to such a position, to bring about the couplingof the fluid drive to the fluid driven drive element of the selectedtype bar by open ation of the fluid control in the region of thatelement 28 Claims, 14 Drawing Figures PATENTED $5? 91975 3. 904. 013

PATENTED'SEP ems SHEET 6 [1F 7 WRITING MACHINES WITH FLUID DRIVE MEANSBACKGROUND OF THE INVENTION l. Field of the Invention This inventionrelates to writing machines and more specifically to writing machines ofthe kind adapted to write characters successively and in successivelines on a record carrier which is fitted over a platen, the charactersbeing written by type carried on type bars which are arranged side byside and pivoted at points lying in an arcuate line, each bar, whenactuated, moving the character carried thereby to a predetermined commonstriking point.

ll. Description of the Prior Art The best known example of a writingmachine of this kind is the ordinary typewriter, in which there is anarrangement of type bars on an arc of a circle which is so oriented withrespect to the platen that the type bars, which may be eithermechanically or electrically operated, are moved, when operated, tocause the type carrying ends thereof to strike the platen at the correctplace. The mechanism required for operating the type bars is expensiveand, in practice, has to be arranged so that the type bars. which arepivoted, may be operated with minimum efi'ort but nevertheless withprecision and also with maximum speed. In writing machines with the typebars mounted in the same way, they have a single, common point ofimpingement on the platen, so that for all type bars and type charactersthe writing process is the same.

Developments in the field of data processing have produced a requirementfor writing machines capable of very high writing speeds (i.e. speeds interms of numbers of characters printed in a unit of time) combined withoptimum writing accuracy and high operational reliability. Normalwriting machines, such as typewriters are capable of writing speeds ofup to about 20 to 24 strikes a second. Other writing mechanisms,operating with so-called golf ball heads are capable of writing speedsof about 20 strikes a second. If writing speeds above such values are tobe attained by writing machines using type bars, it is necessary toreduce the mass of the moving elements, more particularly that of thetype bars, and to use shorter type bars. In this way it is possible toachieve writing speeds of about 30 to 35 strikes a second. However, forsatisfactory and reliable mechanical operation, the type bars must bestrong enough to ensure that they will not be bent during the writingprocess or during their movement, or as a result of the action of themeans used for driving them. In addition, where, as is the normal case,the type bars have bent type heads, there is a liability to theoccurrence of undesired rolling movement because the center of gravitylies outside the pivoting plane passing through the point of mountingand the length of the bars. For this reason, too, the mass of the typebar cannot be reduced below a minimum value which puts an undesirablylow limit to the attainable writing speed.

Known writing machines using type bars have to have a complex drivingmechanism for each type bar. During the outward movement, i.e. movementfrom the rest position, each type bar drive must first of all overcome arestoring force which returns the type bar to its rest position aftereach strike. It is moreover desirable for each type bar to have positiveacceleration when striking. However, because, in known machines withtype bars, the driving impulse for a type bar ceases after about halfthe outward movement, only the kinetic energy which it has then attainedis available to carry it on to the striking position and effect aprinting strike and a substantial proportion of this energy is used upin increasingly tensioning the restoring spring. In addition, it is verydifficult to achieve a lever ratio (mechanical advantage) for each typebar that will result in satisfactory writing in the shortest possibletime and require a minimum amount of energy. The type bar drivingmechanisms occupy so much space as to result in known writing machinesbeing of such size as to make it necessary, practically speaking, forthe type bars to be arranged on only a segment of an arc of a circle infront of the platen. Although it is known to arrange the type bars rounda full circle lying either in front of or underneath the platen, thisleads to a writing machine that is disproportionately large andmoreover, is such that the driving mechanism obscures a view of thewriting. Furthermore, with such an arrangement used in conjunction witha keyboard, the machine is necessarily far from compact. This is becausein a type bar machine with mechanical drive to the type bars from akeyboard, the drive mechanisms are all oriented in the same direction,whereas the driven parts of the type bars must point in differentdirections because of the radial arrangement. In general, the drivingand driven directions coincide only for the central type bar. F or allother type bars the difference in angle increases with the angle betweenthe respective type bar and the central type bar the outermost type barshaving the greatest difference between driving and driven directions. Ifthe angle embraced by the segment in which the type bars (when at rest)lie, is more than and especially if it approaches 360 (i.e. approaches afull circle) it is practically impossible to obtain a clearly visiblemechanically driven typing action in typewriters with constructions asused today.

Further requirements that a writing machine should fulfil concern theguiding of the record carrier on the platen. It is necessary tointroduce the record carrier on to the platen, to lead it away from sameand at the same time to be able to observe the writing process withouthindrance. Record carriers used in data processing include not onlyordinary sheets of paper but also, for example, invoice cards and otherstiff record carriers which do not withstand bending over sharply.

It is thus necessary in known machines to make a variety of compromisesin achieving high-speed writing machines and these compromises result,owing to limitations of the extent to which individual parts can bereduced in size and mass, in severe restriction of the writing speedsattainable. The present invention seeks to overcome these difficultiesand, as will be seen later, does so by making it possible to useunusually short type bars arranged around a full circle immediately infront of the platen at the same time providing, for driving the typebars, a driving arrangement that does not involve expensive mechanismscomprising numerous mechanically moving elements between the type barsand a keyboard.

SUMMARY OF THE PRESENT INVENTION According to the present invention,there is provided a writing machine of the kind in which successivewriting of characters side by side and line by line is effected on arecord carrier led over a platen by means of a plurality of charactercarrying type bars arranged side by side on an arcuate pivot axis andadapted, when actuated, to pivot to effect recording at a commonrecording point, there is provided in common for a plurality of typebars, a fluid drive for producing pivoting move ment of a selected typebar, a plurality of fluid driven drive elements, one for each type bar,fluid control means in the region of each fluid drive element forconnecting the fluid drive to the fluid driven element appropriate to aselected type bar and selector means moveable into one or other of aplurality of predetermined positions in accordance with the type bar tobe selected, said last-mentioned means being arranged, when moved tosuch a position, to bring about the coupling of the fluid drive to thefluid driven drive element of the selected type bar by operation of thefluid control means in the region of that element.

The underlying idea of the invention lies in the realisation that if thetype bars used for effecting writing are reduced in mass. less force isneeded to cause them to pivot without loss of speed of the impelled barsand that it is perfectly practical to construct a fluid drive (thisexpression fluid drive" as herein used includes both pneumatic andhydraulic drives though, as will be apparent later, pneumatic drive ispreferred) arrangement which, though small, is capable of providingforces which are entirely adequate for moving type bars of reducedweight at adequate speeds and fluid drive systems in accordance withthis invention can be readily designed to produce the required forcesand speeds such that adequate kinetic energy of the type bars foreffecting writing is available. In addition there is design freedom toarrange a fluid drive system wherever desirable (in relation to theactual writing mechanism) remotely, if desired because the onlynecessary connections with the writing mechanism are pres sure orsuction lines assigned to all type bars in common. The writing mechanismitself requires merely fluid operated drive elements so that pressure orvacuum acting on them causes them to move. By coupling fluid actuateddrive elements by simple mechanical connections with the respective typebars, rapid and precisely controlled writing movement of the type barscan be achieved. The position of the type bars relative to the fluidcontrol and fluid driven drive elements is immaterial, because no levertransmissions or articulated joints are needed therefor and there are norelatively large masses to be moved and which need to occupy givenpositions. Also, there is no need for strong restoring forces which haveto be overcome. This is in sharp distinction to the usual known writingmachines in which restoring forces are generated by the use ofrelatively strong springs. A further important advantage is that nodifficulties or disadvantages arise, as happens in the case of knownwriting machines, be cause of changes in the direction of movementbetween the keys of a keyboard and a type bar driven by that key.

The fluid drive may be and preferably is an impulse fluid drive withpressure or vacuum impulses at a frequency which can be chosen equal tothe speed of writing or to an integral multiple thereof. The provisionof such an impulse drive makes it possible to realise a particularlysimple control for operating a respective type bar. All that is neededin the fluid drive for this purpose is, for example, actuation of avalve by means of which the pressure or vacuum impulses can betransmitted direct to the fluid control in a selective manner. If theseimpulses have a frequency equal to the prescribed speed of writing or toan integral multiple thereof, then the exact point in time at which thevalve opens is immaterial; all that matters is that a complete pressureor vacuum impulse can act. Naturally, this is especially reliable andsatisfactory in the case in which the frequency of the pressure orvacuum impulses is an integral multiple of the speed of writing.

The pressure or vacuum impulses can be generated by simple pumpingmeans. There may be one such pumping means assigned to all the type barsor there may be more than one, each being assigned to a group of typebars. Such pumping devices may be provided either singly and generatethe pressure impulses and the vacuum impulses inside a working chamberor it is possible, alternatively, to provide two pumping devices whichare displaced in phase, preferably working in phase opposition. Themechanical drive to such pumping means can be effected in a simplemanner by rotary eccentric drives. By regulating the speed of rotationthe impulse frequency can be adjusted to accord with different writingspeeds. With an electrically or automatically actuated writing machineit is possible to adjust the aforesaid speed of rotation to give writingspeeds of the order of strikes a second. This is because a fluid drivemaking only small movements has very little inertia indeed. Moreover,there are no undesirable dead" forces like those due to restoringsprings, to be overcome.

instead of providing a pump or pumps a pulsed fluid drive can beobtained from a constant pressure source, such as an air line, by meansof a rotary valve arrangement, eg one including a rotary sleeve havingperipheral grooves and driven continuously by a rotating shaft theperipheral grooves providing desired connections at the desired timesand for the desired periods between the pressure source and fluidcontrol channels, the grooves covering and uncovering passages in aguide block for the rotary sleeve. Such an arrangement may be extremelyreliable and simple. if the grooves are so arranged that they connectwith a line of constant pressure at regular intervals of time during therotation of the rotary sleeve they can serve to transmit the pressureinto the fluid operated writing mechanism, a pulse-like interruption ofthe transmission being provided by the movement and the limited lengthof the peripheral grooves. It is possible in this way to generatepressure impulses whose sequence is independent of pumping speed. Theimpulses can be led to the drive elements for the type bars from twodifferent directions, so that some act as though they were vacuumimpulses because they act in a direction opposite to that of the others.

Alternatively, of course, pressure impulses could be obtained by meansof linearly movable elements, e.g. slide valves or electromagneticvalves actuated at a given frequency.

As already stated the fluid drive used in carrying out the inventioncould be hydraulic or pneumatic or it may use both principles. This isobvious because any drive effect produced by a pneumatic drive could beproduced by a hydraulic drive or vice-versa. A point to consider is thatthe incompressibility of the hydraulic liquid in a hydraulic drive maybe advantageous as regards the attainment of high speeds of writing.Admittedly, problems of sealing arise, and the handling of liquidspresents problems of a practical nature as compared with the handling ofair. Another advantage of a pneumatic drive is that the specific gravityof air is negligibly small by comparison with that of a suitable liquid.As a result, the intrinsic forces required at the beginning of animpulse in a pneumatic drive medium are considerably smaller than in ahydraulic drive medium, because the small mass necessitates acorrespondingly smaller force to achieve a given acceleration. As statedany fluid drive may be used but, for simplicity and shortness ofdescription, pneumatic drives (which are preferred) will be assumedthroughout in what follows.

ln a further advantageous development of the invention there is providedat least one pressure chamber which is concentric with the arcuate pivotaxis of the type bars and is continuously connected with the drive andits volume is limited by a number of selector slide valves equal innumber to the number of type bars present. The slide valves are arrangedto be moved by releasing them by means of selector devices intopositions in which they open communication between the pressure chamberand the respective drive element.

This further development of the invention makes possible a particularlycompact writing machine. Where the type bars are arranged on a circleor, for example, on two semi-circular segments, they may have assignedto them a special drive segment provided with ducts for carrying thepressure medium, these ducts containing drive elements for the typebars. Where the type bars themselves are arranged on an arcuate pivotaxis those ducts which lead the pressure impulses to the drive elementsof the type bars may advantageously be arranged to emanate radially fromthe pressure chamber and extend in the radial direction. The provisionof a continuous pressure chamber concentric with the pivot axis allowsthe pulsating pressure action of the drive means to be led to thispressure chamber in a particularly simple manner at a desired point ofan overall writing segment with several type bars. The side channelspotentially leading to respectively one drive element for respectivelyone type bar can then branch off from the arcuate pressure chamber. Sucha drive element may be, for example, a piston inside a working cylinder,said piston causing the type bar to which it is assigned to pivot. Ifnow the selector device is so arranged that only one of these branchesfor a drive element of a type bar is opened, then this is enough toensure the complete outward movement of the type bar. As the number ofselector slide valves provided equals the number of type bars present,there being one portion seated in a respective valve-like bore which, incertain positions of the selector slide valves, is connected with theworking space of the type bar drive elements, the sole control operationconsists in the release of the selector slide valve of the respectivelyselected type bar by the selector devices. This enables the slide valvein question to be moved by pressure acting on it when a pressure impulsearises in the pressure chamber until the channel from the arcuatepressure chamber is in communication with the working space for thedrive element of the selected type bar.

In another development of the invention two concentric pressure chambersare provided, of which one is continuously connected with second driveelements for the type bars and, when pressure acts, produces a movementof the type bar (which it is assumed has just been pivoted away from itsrest position) back into that position. In this way it is possible toproduce the return movement of the type bars as well as their outwardmovement by means of pressure impulses. A double ended lever, forexample, may be provided. Outward drive of a type ,bar is provided byone end of the lever as a result of pressure in the first pressurechamber, while the second lever arm is acted on as a result of pressurein the second pressure chamber. Thus no suction effect is required toreturn type bars into their rest positions and a somewhat more uniformmode of working of the writing mechanism is achieved.

Where the pressure is generated in pulses it is necessary to equalisethe pressure between the working chambers of the drive elements andatmosphere during the intervals elapsing between individual pressurepulses. For this purpose a connection of a concentric pressure chamberwith atmosphere can advantageously be made via the drive. Thisconnection can, for example, be effected by control slide valves whichare coupled with the drive shaft and which, in given positions of saidshaft open a connection between the concentric pressure chamber andatmosphere. This is particularly advantageous where two pumping devicesworking in phase opposition are provided. The common drive shaft forthese pumping devices then drives the two control slide valves, so thatthese work positively at a speed corresponding with the opposed phaseoperation and, for example, each may, in one extreme position connectone pumping device with atmosphere. Where the drive is effected by arotary sleeve with peripheral grooves the connection of the pressurechamber with atmosphere can be run via the rotary element. For thispurpose the element is suitably constructed as a sleeve rotatablyarranged on a cylindrical pin or rod, with a connection provided betweena peripheral groove and the space between the sleeve and the rod or pin.if this space communicates with atmosphere, as is easily arranged, thenthis will provide the required connection between the pressure chambersand atmosphere in given positions of the drive.

The choice between returning a type bar into its rest position either bysuction or by pressure action leads to a choice between two differentprinciples of working. When only one pumping device utilising pressureand vacuum is used, the excess pressure that arises in the pressurechamber when the type bar reaches the writing position is equalised withatmosphere by arranging the respective drive element to open a boreleading to atmosphere. Subsequently, reduced pressure is generated inthe working space of the drive element. When the type bar has performedonly a small part of its return path the drive element causes the boreleading to atmosphere to be reclosed, and the reduced pressure acts onthe type bar via the drive element. Once the reduced pressure hasreached a certain value it overcomes the retaining force with which theselector slide valve is held in its selected position. If the type barhas not yet reached its rest position and if the drive element stillexerts a compressing action, the pressure is allowed to escape toatmosphere, for which purpose a connection between the working space andatmosphere is provided on the selector slide valve close to its restposition. In the corresponding working position of the drive that isthen reached, the vacuum can equalise with the outside pressure via aconnection passing through the drive. In this case a single chamber thusacts alternately as a pressure and as a vacuum chamber.

Where use is made of two pumping devices working in opposite phase or asource of constant pressure controlled by valve means to provide pulsesthe pressure chamber is connected to atmosphere via the drive in itsvacuum position. This is because the vacuum position of the drive isthat position in which the respectively actuated drive element for atype bar has been restored into its rest position. Irrespectively ofwhether this ensues by the action of pressure or vacuum, the normalpressure relationships must be re-established before the next work cycletakes place in order to ensure a satisfactory utilisation of the workingcapacity of the pneumatic drive. By arranging the rotary element for thedrive to open a channel when in the vacuum position, pressureequalisation between the pressure chambers and atmosphere can be ensuredin a very simple manner.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is illustrated in andfurther explained in connection with the accompanying drawings, inwhich:

FIG. 1 illustrates one form of writing mechanism in accordance with theinvention and having a pneumatic drive provided by a simple singleacting diaphragm p ps FIG. 2 is a composite view of the writingmechanism of FIG. 1 looking in the direction of the arrows II, III andIV of FIG. 1,

FIG. 3 is a graphical figure showing pressure distribution and amplitudeof motion in the pneumatic drive of FIG. 1 during a given portion of theoperation,

FIG. 4 shows graphically the pressure distribution of the working volumeof the writing mechanism of FIG. 1, during the given portion of .theoperation,

FIG. 5 shows another form of a writing mechanism in accordance with theinvention with a pneumatic drive provided by two diaphragm pumps workingin opposite phases,

FIG. 6 shows a further form of writing mechanism in accordance with theinvention with a pneumatic drive to which a constant pressure is fed andwhich generates a displaced-phase pressure effect,

FIG. 7 is another view of the pneumatic drive of FIG. 6 taken on theelevation VII-VII of FIG. 6,

FIG. 8 is a representation of a control element in the pneumatic driveshown in FIG. 7,

FIGS. 9 to 12 are sectional views taken on the lines IX, X. XI and XIIof FIG. 8 of the control element of FIG. 8,

FIG. 13 is an explanatory working diagram of a writing mechanism asillustrated by FIG. 6, and,

FIG. 14 is an overall view of a writing machine in accordance with theinvention.

DETAILED DESCRIPTION The figures illustrating writing mechanisms show ineach case a type bar and its driving elements in side elevation. Theelements common to all type bars, which in correspondence with thearrangement of all the type bars are in part constructed in the form ofan arc of a circle, are therefore shown in section. These relationshipsare revealed by a comparison of the writing mechanisms with the overallview shown in FIG. I4.

FIGS. 1 and 2 show a type bar with associated pneumatic drive andpneumatic control in relation to a platen 24. There is a group of typebars arranged on an arc of a circle which is disposed in such a way thatthe pneumatic drive and the nature of the control common to all typebars can be seen. In addition, the type bar 10 with its associatedmovable drive elements can be seen. Individual parts which areunnecessary for an understanding of the invention, e.g. screwed joints,bearings and couplings are not illustrated in the figures.

The type bar 10 carries at its outer free end a type character 12. Inthe rest position it is held by an arcuate magnet strip 50 common to allthe type bars. It is mounted on an arcuate bearing axis 16 shown insection in FIG. 1. When actuated the bar 10 pivots on the pivot axis 16and swings its type character 12 along a circular path 20 to strike theplaten 24. The arcuate bearing axis 16 is supported by a type barsegment 48 which has a guide slot for each type bar. Thus the type bar10 can pivot inside the slot 18. At its pivot end on the bearing axis16, the type bar 10 has gear teeth 14 engaging in corresponding teeth 28on an intermediate bar lever 26. This intermediate bar lever 26 ispivoted on a further arcuate bearing axis 30 concentric with the axis 16and has, diametrically opposite the teeth 28, further teeth 32 engagingteeth 34 on a drive lever bar 36 which is pivotably mounted on a furtherarcuate bearing axis 38. A slot 42 provided for each drive bar in adrive segment 54, permits pivotal movement of the drive lever bar 36.This movement is imparted by a piston 46 which is driven in manner to bedescribed later. A buffer stop 22 made of elastic or hard resilientmaterial is secured to the drive segment 54. The upper end of this stopis shaped as shown to prevent chattering of the type bar 10 directly onthe platen 24 and ensures an interference-free return movement of thetype bar 10 allowing striking of the platen 24.

An arcuate arrangement of selector bars is provided radially outside thetype bar segment 48 and in front of the drive segment 54. The manner inwhich the pneumatic control for the type bars I0 is actuated will belater described but the selector bars work much in the same known way asthe corresponding parts of a teleprinter for example. They are arrangedin a surrounding ring, and can act on the control of every one of thetype bars. Cut-away portions in the selector bars in accordance with aprescribed code ensure that each particular mutual positionalcombination, if set up, procures actuation of a selected type bar. Theway in which the selected type bar is moved is yet to be described.

The pneumatic drive is provided underneath or outside the type barsegment 48 and the drive segment 54 and is secured to a bearing frame86. The bearing frame 86 is optionally displaceably, and is mounted onbearing rods 90 and 94 by means of guides 92 and 96. The pneumatic driveis provided by a diaphragm pump with a pneumatic chamber 98 in which isa diaphragm 100 which is caused to vibrate from underneath by aneccentric rotary drive. It rhythmically compresses the air in thepneumatic chamber98 so that a pulse-like pneumatic driving force isgenerated for the type bars.

The following description gives the mode of functioning of thearrangement illustrated in FIGS. 1 and 2 and also describes furtherindividual components. To begin with the generation of the pulsatingdriving force will be described together with its effect on the controland the drive of the type bars 10 in accordance with the settings of theselector bar arrangement 72.

The walls of the pneumatic chamber 98 are constituted by surfaces of thebearing frame 86, a frame 162 and a diaphragm plate 104 attached to thediaphragm. The said diaphragm 100 is clamped peripherally between thebearing frame 86 and the frame 102. it may consist, for example, of twoair-impermeable material layers on whose top surface is a counterplate101, the diaphragm 100 between itself between this plate 101 and thelower diaphragm structure rests with the periphery of the plate 104 onthe lower edge of the frame 102. The diaphragm plate 104 is connectedwith the interior of a cylindrical guide sleeve 116 via a flexibleairtight connection 114, which forms a duct 123. The guide sleeve 116 issecured to an eccentric bushing l 18 serving for the eccentric guidingof a square sectioned drive shaft 120. 1n addition, the diaphragm plate104 is coupled directly to the guide sleeve 116 via rocker arm links108, of which only one is shown in FIG. 1. In the position shown of thedrive shaft 120 the pneumatic chamber 98 possesses its maximum volumeand the air space above the diaphragm 100 is connected with atmospherevia a diaphragm bore 121, the duct 123, a duct 124 in the guide sleeve116 and a bore 122 in the eccentric bushing 118. The rocker arms 108 aremovably coupled to the diaphragm plate 104 with an extension via a pin110. When the bushing 118 is turned by the drive shaft 120 anoscillatory movement of the diaphragm 100 ensues as a result of therhythmic rise and fall via this coupling A pressure equalisation betweenthe pneumatic system and the outside can alternatively take place viathe flexible line 114 or the duct 123, in each case in the operationalposition shown in FIG. 1.

The pneumatic chamber 98 is connected with the type bar segment 48 via apressure line 80. The pressure line 80 is secured in the type barsegment 48 and in the bearing frame 86 at both ends by means of screwedjoints 82 and connecting elements 84 respectively. A duct 88 is providedin the bearing frame 86 and connects the connecting line 80 with theinterior of the pneumatic chamber 98, so that during each upwardmovement of the diaphragm 100 an increase in pressure in the bore 60 ofthe type bar segment 48 is generated. This bore 60 is assumed to becommon for all type bars, but, alternatively, there may be a number ofsuch bores, each assigned to one respective group of type bars, so thateach type bar is connected with the pneumatic drive by the shortestpossible route.

When a pulse-like increase in pressure is generated in the bore 60 itarises also in a pressure chamber 58 via a transverse bore 52, whichchamber runs in arcuate manner through the entire type bar segment 48and is assigned to all type bars. An oscillating or pulse-like pneumaticpressure is therefore available in this pressure chamber 58. Thefrequency of the pulsing can be adjusted (by adjusting the speed ofrevolutions of the drive shaft 120) to correspond to a prescribedwriting speed or an integral multiple of a prescribed writing speed.

Each type bar has a control assigned to it formed by channels providedin the driving segment 54 and each opened and closed by a selector slidevalve 69 in a radial bore 62. In this way the already described pistons46, which causes the drive lever bars 36 to pivot, are actuated.

The control process for actuating the type bar shown in FIG. 1 isinitiated by bringing the arcuate selector rails of the arrangement 72into a mutual position in which a flattened portion at the lower end ofthe selector slide valve 69 can fall through a gap formed by thecut-away portions of the selector bars. To carry out the adjustmentmovement the selector bars can be displaced mutually by an amountdetermined by their code around the entire arcuate arrangement of alltype bars. For this purpose they are secured to the drive segment 54 bymeans of a bearing surface 78 or a bearing element 76 and several guidepins 74. When the selector rails are located in the position in whichthe flattened portion 70 shown can fall into a gap formed by theircut-away portions, then the selector slide valve 69 shown is moveddownwards within the capture range of a magnetic strip 79, which thenholds it. A branch bore 64 is now in communication with the pressurechamber 58 and the pulsating pneumatic pressure in said pressure chamberacts on the piston 46, which is in a widened bore extension 44 of thebore 64. The piston 46 accordingly moves towards the right from the restposition shown in FIG. 1. The portion 40 of the drive lever bar 36 is inthe cut-away portion 47 of the piston 46 and accordingly the drive leverbar 36 is moved pivotally, swinging clockwise about the arcuate bearingaxis 38. This movement causes a rotation of the intermediate lever bar26 on its arcuate bearing axis 30 and the type bar 10 is caused to pivotabout the arcuate bearing axis 16 so that the type character 12 swingsto the platen 24 along the path 20. The impulse like control of thepneumatic pressure in the arcuate pressure chamber 58 and the initiallyacting retaining force of the magnetic strip 50 causes the type bar 10to start its swing suddenly, so that, when it moves it does so fast andthere is adequate kinetic energy to produce a good strike on the platen24. As already mentioned the buffer stop 22 provides a springy stop forthe type bar, preventing chattering of the character 12 on the platen 24and initially return movement of the type bar 10.

The control of the final part of the movement of the type bar 10 ensuesin the described manner to the point where the piston 46 during itsoutward movement, provides access to a bore 65 so that excess pressurepresent in the pneumatic system escapes to atmosphere through the bore65. When this happens the driving force which previously acted directlyon the piston 46, disappears. However, at this time, the type bar 10still has kinetic energy so that it continues to move towards the platen24 and strikes the buffer stop 22. The latter is so adjusted that thetype character 12 can strike the platen 24 sharply, the spring action ofthe buffer stop 22 at once initiating the return movement of the typebar 10. As the intermediate lever bar 26, the drive lever bar 36 and thepiston 46 are positively coupled with the type bar 10, these elementsfollow the movements of the said type bar 10, and the piston 46 is alsomoved back. The pneumatic drive, which now generates a suction effect,aids the return movement of the piston 46. In the meantime the diaphragmhas been moved downwards by the further rotation of the drive shaft 120,so that the volume of the pneumatic chamber 98 now once more increasesand a vacuum is formed in the space formed by the bore 60, thetransverse bore 52 and the arcuate pressure chamber 58. This augmentsthe return movement of the piston 46. During these events the selectorslide valve 69 is still held in its lower position by the magnetic strip79. The retaining force of the magnetic strip 79 is so chosen that thereturn of the selector slide valve 69 occurs suddenly and only when acertain vacuum is reached in the arcuate chamber 58. At this point intime, however, the type bar will already be close to the rest position(shown in FIG. 1 and within the capture range of the magnetic strip 50.During these events the piston 46 is once more moved to the left and airpresent in the bore 44 or in the bore 64 is released through a duct 66to atmosphere in correspondence with its return movement if the selectorslide valve 69 has meanwhile been moved back. This is made possible byproviding a reduced diameter portion 68 on the selector slide valve 69.In this way the arrangement once more assumes the rest position shown inFIG. 1, in which a pressure equalisation between the pressure chamber 58and atmosphere occurs via the diaphragm bore 121, the flexible duct 123and the mutually opposite bores 124 and 122 of the rotary drive.

FIG. 2 shows an arrangement with several type bars 10 in varioussections "-11 and III--III and in the elevation IV, as indicated in FIG.I. The pneumatic drive on the underside of the type bar arrangement isshown in side elevation. From the right-hand section IIII the nature ofthe feeding of the pulsating pressure into the arcuate pressure chamber58 via the connecting line 80, the bore 60 and the transverse bore 52 isclearly to be seen. The parts of the pneumatic drive on the underside ofthe arrangement shown illustrate the assignment bf the pneumatic driveas individual units to all type bars 10 present in the side elevation ofFIG. 2.

Section IIII shows the type bar segment 48 in partsectionalrepresentation. At its upper non-sectional end the slots 18 for theguide of the type bars 10 can be seen. Section III-III, which isdisplaced somewhat to the right by comparison to the Section IIII ofFIG. 1, but in FIG. 2 is shown on the left next to Section IIII, revealsthe arrangement of the selector slide valves 69 in their bores 62 in thedrive segment 54. In addition there can be seen the flattened portions70 of the selector slide valves 69 which, in dependence upon the settingof the arcuate selector bar arrangement 72, can fall into gaps formed bya particular mutual disposition of the cut-away portions 73.Furthermore. the coded distribution and dimensioning of the cut-awayportions 73 on the inner periphery of a selector bar can be seen. Bymeans of a slight displacement in the peripheral direction the selectorbars can be adjusted mutually in a respective manner such that theflattened portion 70 of only a single prescribed selector slide valve 69can engage lockingly in a gap. Arrows indicate the movement of theselector slide valves 69 in the radial direction.

It will further be seen how the drive segment 54 is po sitioned withrespect to the type bar segment 48 and the way in which the arcuatepressure chamber 58 runs between the two segments 54 and 48. As alreadyexplained a pulsating pressure is continuously available, which pressureproduces the pneumatic drive.

Finally, the side elevation IV, shows several type bars 10 with theirtype characters l2 and enables the nature of the overall writingarrangement with respect to the platen 24 to be understood.

FIG. 3 is a curve connecting pneumatic pressure p and displacement a ofthe diaphragm (ordinates) with the angular position in time wt(ahscissae) of the drive phragm to move up and down, and these twomovements' in different directions produce excess and re- (ill shaft I20relative to a zero position. The curve ignores pressure equalisationoccurring in any particular position. The rotation of the drive shaft120 causes the dia duced pressure respectively relative to atmosphereand with a frequency that is dependent on the speed of rev olution ofthe drive shaft 120. The representation in FIG.3, shows, as the initialstate corresponding to the position shown in FIG. I, a vacuum having thevalue -p, which, as a result of the rotation of the drive shaft I20 by1r is converted into a pressure +p, with the diaphragm passing throughthe central position when the pressure is zero. In this representationrelative values are concerned whose magnitudes p and +p state a reducedpressure and excess pressure relative respectively to normal pressure.If no allowance is made for pressure equalisation or mechanicalside-effects, a pressure variation with time of practically sinusoidalform would be generated in the pneumatic chamber 98, so that the curveof FIG. 3 is also a curve of displacement +A and A respectively of thediaphragm 100.

FIG. 4 typifies the actual course of the pressure in the pneumaticchamber 98 and in the arcuate pressure chamber 58 and, assuming anactuated selector slide valve 69 also shows the the time-varying forceacting on the piston 46 which ultimately causes the type bar 10 to move.This representation assumes that, as a consequence of ceretainmechanical tolerances and because a certain time is required for thecontrol movement of the selector slide valve 69 and the related increase in volume of the pressure chamber 58 to occur. the increase inpressure in front of the piston 46 begins at a point in time thatdiffers from zero time and zero angular position of the drive shaft 120.Following the pressure equalisation with atmosphere that ensues in thisposition, the pressure increases to a peak value of +Pk, when the piston46 has already moved in its bore 44 and the type bar 10 has already beenmoved towards the platen 24. During this part of the curve (J to +Pk)the pressure continues to rise continuously in front of the piston 46despite the size of the pneumatic chamber 98, because the volume that itfrees is considerably less than that of the pneumatic chamber 98. Thepressure valve +Pk is also higher than the value +P shown in FIG. 3,because during actual functioning a pressure equalisation takes place inthe starting position shown in FIGv l and the compression process beginswith at' mospheric pressure as the starting pressure.

The overall design is such that on reaching the pressure +Pk the driveto the type bar 10 comes to an end. At this point in time the bore 65 isopened by the piston 46 as already described, so that'a comparativelysteep fall of pressure occurs in the system.

As already explained, the final portion of the movement of the type bar10 ensues by virtue of the kinetic energy that has been imparted to it.Following striking of the platen 24 by the type character 12, the bufferstop 22 initiates the return movement of the type bar 10 and thepositive link between the type bar I0 and the piston 46 via theintermediate lever bar 26 and the drive lever bar 36 causes the piston46 to be moved backwards and closes the opening to the bore 65. Thefurther rotation of the drive shaft causes the diaphragm 100 to movedownwards, so that a vacuum is formed in the control system and in thearcuate pres sure chamber 58, as is shown in FIG. 4 by the negativecourse of the pressure eurve to a negative peak Pk. The negativepressure part of the curve to the extreme value Pk is not necessarilyand is not shown as symmetrical lth respect to the abovedescribedpositive course of the pressure curve. At a predetermined pressurebetween Zero or atmosphere and the value Pk the selector slide valve 69responds and overcomes the retaining force exerted by the magnetic strip79, so that the reduced diameter portion 68 of the selector slide valve69 once more creates a connection between the bore 64 and the duct 66,to open the piston chamber to atmosphere.

The further course of the curve between Pk and zero now ensues with themechanical parts of the apparatus in their rest positions, the furtherrotation of the drive shaft 120 alone governing the variation inpressure. When the drive shaft 120 inside its sleeve 116 once moreapproaches the position 211' shown in FIG. I, the pressure equalisationbetween the pneumatic chamber 98, and atmosphere ensues via thediaphragm bore 121, the flexible joint 114 and the bores 122 and 124, sothat the atmospheric pressure is restored in the pneumatic controlsystem, as is indicated in FIG. 4 by the steeply ascending part of thenegative portion of the pressure distribution curve.

FIG. 5 shows an embodiment in which what may be called a two-partopposed phase drive is provided. In FIG. 5 there are many parts whichcorrespond with parts of the apparatus in FIG. 1. Such parts areidentifled in FIG. 5 by references the last two figures of which are thesame as the two-figure references used for the corresponding parts inFIG. 1. Here there are two pneumatic chambers 298 and 298a which providepumping action as the result of a common rotary drive. Control of thepressure relationships in the two pneumatic chambers 298 and 298a iseffected by means of two control slide valves 326 and 3260 in bores 344and 344a in a bearing frame 286. The bearing frame 286 holds thetwo-part pneumatic drive between two side plates, transverse rods 290and 294 being provided as bearing elements between the side plates and,for the purpose of providing asymmetrical drive, certain moving partsare present in duplicate in a manner to be described later. They areconnected with one another by means of moving transverse rods, which areshown shaded in FIG. 5. All this will be clearer later.

The writing mechanism shown in FIG. 5 together with the pneumaticchamber 298 is generally similar to that already described, there beinga generally similar pneumatic control. The second pneumatic chamber 298aserves merely to return the type bar 210 to its rest position on amagnetic strip 250 following a strike, so that the generation of vacuum(as in the embodiment of FIG. 1) is unnecessary for this purpose, thereturn of the type bar 210 being also effected by pressure. The twopneumatic chambers 298 and 298a work in phase opposition, i.e. they actwith their phases displaced by 180 or 11' respectively. This ispreferred but is not essential for, as will be apparent later, adifferent relative phase displacement could be used.

The process of pneumatic control for the outward movement of the typebar 210 (mounted in a type bar segment 248) is effected in similarmanner to that already described for FIG. I. In accordance with the adjustment of a selector bar arrangement 272, which is secured to thedrive segment 254 by the intermediary of the parts 276 and 278 and isadjusted on guide pins 274, the flattened portion 270 of a selectorslide valve 269 provided for each type bar 210 can engage lockingly in agap of the selector bar arrangement 2'72 and can then be retained on amagnetic strip 279. Thus, when pressure is produced in the pneumaticchamber 298, the pressure generated is passed to an arcuate pressurechamber 258 via a duct 288, a connecting line 280 secured by means ofconnecting and union elements 284 and 282, a bore 260 and a transversebore 252, and, as a result of the descent of the selector slide valve269 in its bore 262, passes through a bore 264 to act on a piston 246 ina bore 244.

In this writing mechanism in which the return movement of the type baralso ensues under positive pressure, the pressure chamber used for theoutward movement will be hereinafter termed the call chamber, and anarcuate pressure chamber used for the return movement will behereinafter termed recall chamher.

The effect of the pressure on the piston 246 drives the upper part 240of the drive lever bar 236 to the right. This lever bar is, in theconstruction of FIG. 5, doubled-ended and a slot 242 is provided for itin the drive segment 254. The lever bar 236 accordingly swings clockwiseon its arcuate bearing axis 238, and causes the type bar 210, (shownbroken-away in FIG. 5) to swing round towards the piston (not shown inFIG. 5), the drive to the type bar being, as in FIG. 1, through toothgearing on the lever bar 236, the intermediate lever bar 226 and thetype bar 210. The lower arm 241 of the drive lever bar 236 of coursemoves to the left displacing to the left a piston 247 in a bore 245.While compression in the call chamber 258 acts on the type bars 210 viathe selector and drive elements until a connection to atmosphere isestablished via a bore 265, simultaneously expansion in a recall chamber259 has no effect on the type bar 210 by virtue of a connection 342a toatmosphere produced by the control slide valve 326a. The recall chamber259 is not used to aid the call-up chamber 258, because suctiongenerated inside the former would act not only on the selected type bar210 but on all type bars, selector slide valves 269 being assigned onlyto the call chamber 258.

During the return movement of the type bar the full compression pressurein the recall chamber 259 acts on all pistons 247. This pressure is ledto it via a duct 288a a connecting line 2800 secured by means of unionand connection elements 282a and 284a and a bore 260a. However, as allpistons except one are located in the rest position, only this onepiston 247 can be moved. The reduced diameter 268 of the selector slidevalve 269 together with the bore 266 leading to atmosphere serves thefunction of equalising the pressure during the return movement of thepiston 246 as already described for arrangement of FIG. 1.

The two pneumatic chambers 298 and 298a are controlled by a commonrotary drive. Each is constructed similarly to the chamber 98 of FIG. 1and each has a diaphragm 300 or.300a with diaphragm plates 301 and 304or 301a and 304a. Respective frames 302 and 3020 are provided havingrespective extensions 312 and 312a to which are imparted oscillatorymovement. The rotary drive consists essentially of a square sectioneddrive shaft 320 which may be arranged eccentrically inside a sleeve 318.This sleeve 318 is provided with four crank elements which are mutuallydisplaced by about of which only two, 306 and 307 are revealed in thesection shown in FIG. 5. The crank element 306 is coupled directly witha rocker arm 322 at a pivot pin 330, so that as a result of the rotationof the drive shaft 320 inside the eccentric sleeve 318 an oscillatorymovement is transmitted to links 338 on pivot axes 336 and 310, anddrive the extension 312 of the diaphragm plate 304 directly. The tworocker arms 332 are each mounted on one bearing point 334 in the bearingframe 286. A similar movement is imparted to the other diaphragm plate304a via connecting bars 340 which couple the rocker arms 332 with likerocker arms 332a each secured to the bearing point 3340 in the bearingframe 286. These second rocker arms 32211 are coupled via links 3380 onpivot axes 336a and 3100 with the extensions 3120 on the diaphragmplates 3040 of the pneumatic chamber 2980. This drive coupling effects apositive phase-displaced working on the diaphragms in the two pneumaticchambers 298 and 2980.

The control slide valves 326 and 326a are provided for pressureequalisation in the pneumatic chambers 298 and 2980 and each has aportion of reduced diameter as shown. This portion can selectivelyconnect a duct 324 or a duct 342a with atmosphere in dependence on theposition of the respective control slide 326 and 326a respectively. Theducts 324 and 3240 lead to the pneumatic chambers 298 and 298arespectively, so that the pressure equalisation in the pneumaticchambers 298 and 29811 and hence in the call chamber 258 and the recallchamber 259 takes place through this channel. The reciprocating drive ofthe control slides 326 and 326a is effected on their outer projectingends 360 and 3600. These projecting ends 360 and 360a are engaged by twoconnecting slide valves 354 which can move horizontally (as viewed inFIG. 5) by virtue of a pin and slot connection comprising a pin 358 anda slot 356. The second crank ele ments 307 on the eccentric sleeve 318causes direction-changing levers 348 to move, namely on an articulatedjoint 346 about a bearing point 350, on which the direction-changinglevers 348 are connected with the bearing frame 286. Thedirection-changing levers 348 are connected with one another via atransverse rod 352, on which their coupling with the control slidevalves 326 and 326a via the connecting sliders 354 also ensues.

The rotary device shown in FIG. 5 is symmetrical. At both its endsfacing a respective side plate the drive shaft 320 is provided with twocrank elements 306 and 307. Accordingly, two rocker arms 332 and 332a,too, are provided on either side of the pneumatic drive. A connectingslide valve 354, a direction-changing lever 348 and a connecting rod 340are similarly provided in duplicate. These elements are so connected asto provide a symmetrical drive by means of transverse rods 336, 336a and352, which are shown in section in FIG. 5.

The action of the apparatus shown in FIG. 5 is now easy to appreciate.Rotation of the drive shaft 320 produces a rhythmic generation ofpressure pulses in the pneumatic chambers 298 and 298a. As alreadydescribed a respective lever arm 240 or 241 of the drive lever bar 236is moved to the right by the appropriate piston 246 or 247. At the sametime the respective other lever arm with its associated piston is movedto the left. During these events the control slide valves 326 and 3260are driven directly by the drive shaft 320 in such a way that pressureequalisation as has already been described with reference to FIG. I,ensues via the ducts 342 and 342a. It needs to be considered, whereapplicable. that the respectively lockingly engaged selector slider 269initially must be brought into its rest position by a suction effectlinked to the expansion of the pneumatic chamber 298 while the duct 342is closed off.

By suitably dimensionally the control slide valves 326 and 326a themovement of the type bar 210 and its type character 212 towards theplaten may be made such that at the decisive moment when the typecharacter 212 is just about to strike the platen. the drive to the typebar 210 ceases so that, at the moment of striking, the type bar 210 hasonly the kinetic energy imparted to its during its outward movement. Inthis way it is ensured that the record carrier on the platen is not hittoo hard during the writing process, but just hard enough for optimumwriting. To achieve this it is merely necessary so to dimension thecontrol slide valves 326 and 326a that, at the correct moment, duringthe outward movement of the type bars 210, the connection between theduct 324a and atmosphere is opened. In fact by having control slidevalves 326 and 326a having different dimensions, and selecting the mostsuitable ones for insertion it is possible to have a machine which canbe thus adjusted to suit different requirements as regards writingspeed, writing quality and writing intensity or where required, to workwith a certain phase displacement between call and recall chamber.

FIG. 6 shows an embodiment of a writing mechanism in which, again, adouble ended drive lever bar 436 is used. Here, as in FIG. 5, partscorresponding with parts in the embodiment of FIG. 1 are indicated withreferences the last two figures of which are the same as the two-figurereferences used for the corresponding parts in FIG. 1. In FIG. 6 thetype bar segment is referenced 448 and is secured to a retaining device449. The working of the type bar movement is similar to that de scribedin FIG. 5, but an alternative form of a selector bar arrangement 472with selector bars adjustably secured on the drive segment 454 by theintermediary of 478 is used. A different pneumatic drive arrangementwhich works with continuously fed compressed air and is secured on aretaining plate 512 is provided. Com pressed air supplied from an airline 516 is divided into pressure pulses by a rotating control sleeve500 and is fed respectively to one or other of two different connectinglines 480 and 465 secured with union and connecting elements 482 and484. For this purpose the control sleeve 500 has peripheral grooves 504which, in different positions of the rotating control sleeve 500, makethe difference air connections. The peripheral grooves 504 are sodimensioned that, in conjunction with the inner wall of the body 514,channels are formed which move past supply and discharge bores 506, 508,510 in the said body 514 as the control sleeve rotates. In this wayconnections to these bores are established. for the required controlperiods.

In the writing mechanism shown in FIG. 6 a call chamber 458 and a recallchamber 459 are provided in a drive segment 459. These chamberscommunicate with the connecting lines 465 and 480. The call chamber 458is connected with the connecting line 465 via a transverse bore 461 anda duct 463. As in the previously described embodiments. pressureequalisation with atmosphere takes place in certain positions of thepneumatic drive, by the control sleeve 500. This is done by providingthe control sleeve 500 with at least one radial bore 526 (FIG. 8),through which one or its peripheral grooves 504 is put intocommunication with atmosphere in predetermined positions via a duct provided between the control sleeve 500 and the drive shaft 502.

The functioning of the writing mechanism illustrated in FIG. 6 is onerotation of the drive shaft 502 will now be described. Assume initiallythat the call chamber 458 is not in communication with the pressure line516. This will be the case when control sleeve 500 is in a position inwhich none of its peripheral grooves 504 makes such a connectionpossible. However, the call chamber 458 is connected with a bore 506 viathe ducts 461 and 463 and the line 465, which bore 506 is, in theinitial position of the drive shaft 502 under consider ation, connectedwith atmosphere via one of its peripheral grooves 504. This connectionis blocked when the drive shaft 502 turns through a small angle andremains blocked until a position of about l50 with respect to thestarting position has been reached. The selector bar arrangement 472 isso adjusted that, during the rotation phase from to 30 the gap that itforms is located underneath an intermediate element 470, so that thelatter can lockingly engage in it and be retained by the magnetic strip479. The intermediate elements 470 are held on a magnetic strip 471 intheir rest position (shown in FIG. 6) said strip 471 being secured tothe typ bar segment 448. When a rotation through 30 has ensued the callchamber 458 becomes connected with the pressure fed in through the line516, this connection being made via a peripheral groove 504 in thecontrol sleeve 500, the line 465 and the ducts 463 and 461. The pressurein the call chamber 458 now actuates that selector slide valve 469 whoseintermediate element 470 happens to be opposite the gap formed with theselector bar arrangement 472. By virtue of a locking engagement in thisgap the selector slide valve 469 gives access to a bore 464 leading tothe piston 446, so that the piston 466 is moved to the right from theposition shown in FIG. 6. During this event the piston 446 acts on onearm 440 of a drive lever bar 436, so that said bar pivots clockwise onits axis 438 and the type bar 410 is moved from the magnetic strip 450towards the platen 424 by means of the toothed intermediate lever bar426. The type character 412 accordingly moves over the arc of the circle420 and strikes the record carrier on the platen. During this even thelower lever arm 441 of the lever bar 436 causes a piston 447 to be movedto the left from the position that it occupies in FIG. 6, so that thevolume in front of the piston 447 in the recall chamber 459 and in thebore 445 connected with it diminishes. To prevent compression takingplace during this action, the recall chamber 459 is connected withatmosphere via a peripheral groove in the control sleeve 500.Alternatively, pressure equalisation can ensue upwards as soon as thelower part of the selector slide valve 469 has moved past the bore 445and its reduced diameter portion 464 faces the bore 445.

Pressure is fed to the call chamber 458 until the control sleeve takesup its l position approximately. It is then cut off by the appropriateperipheral groove 504 in the control sleeve 500. The type bar 410however continued along its path because of the kinetic energy it hasgathered and completes its writing movement automatically, while thepiston 446 moves until an edge 466a of its bore is reached, after whichpressure equalisation with the space in front of the piston 447 takesplace. The call chamber 468 is once more connected with atmosphere afterfurther rotation of the control sleeve 500 via the ducts 461, 463, theconnecting line 465 and a periphal groove 504 in the control sleeve 500.

The second half of the rotation of the control sleeve 500 serves for thereturn movement of the type bar. Similar processes now take place inrespect of the recall chamber 459 as have already been described for thecall chamber 458. However, the movement of the drive lever arm 436 nowensues simultaneously with the return movement of the selector slidevalve 469. For this purpose the call diameter 459 is connected with thepressure line 516 via the connecting line 480 and a peripheral groove504 in the control sleeve 500. Previously, however, at the l position ofrotation, its connection with atmosphere is eliminated. At the 2 l 0position of rotation increase in pressure takes place and is maintaineduntil rotation to about 300 occurs. As a result. the piston 447 is movedto the right and hence the drive lever bar 436 is caused to pivotanti-clockwise to its lower lever arm 441, so that the type bar 412 isreturned by its rest position on the magnetic strip 450. At the sametime the selector slide valve 469 is pushed upwards, so that it entrainsthe intermediate element 470 coupled with it in the region of a cut-awayportion 473 in the drive segment 464 until it once more reaches thecapture range of the magnetic strip 471, and is once more retained inits rest position. At this stage the bore 464 in front of the piston 446is connected with atmospheric via the connection formed by the reduceddiameter portion 468 of the selector slide valve 469 in the bore 460.

FIG. 7 is a view of the pneumatic drive of FIG. 6 taken on the lineVII-VII of that figure. Referring to FIG. 7 the sleeve 500 of FIG. 6 isarranged in a block 514 on the drive shaft 502 and can be continuouslyrotated by it. It may, for example, be held on one end by a disc 522,while its other end is retained by a nut 524. Several bores 510 areprovided in the block 514, some proceeding radially to the controlsleeve 500 and some being in the longitudinal direction of the sleeve.In accordance with their functions certain of these bores are sealedwith respect to atmosphere with suitable sealing element. The lines 465and 480 (FIG. 6) leading to the type bar communicate with and are abovethe vertical bores 506 and 508. The arrangement may be mounted on theplate 512 which may be part of the framework of the writing machine.

FIG. 8 shows the control sleeve 500 itself. It has four peripheralgrooves 504, which are so arranged and of such length that duringrotation of the sleeve they provide through the bores 510 the control ofa writing operation, as already described with reference to FIG. 6.FIGS. 9 to 12 illustrate, by way of example, a possible arrangement ofthe four peripheral grooves 504. These figures are, respectively, viewson the sections IX, X, XI and X11 of FIG. 8. Other forms andarrangements of grooving are, of course, possible.

FIG. 13 is a diagram illustrating the working of a writing mechanism.for example as already illustrated and explained with reference to FIGS.5 to 12. The representation of FIG. 13 covers one rotation of the driveshaft 502 between 0 and 360, and the key to the diagram is given beneathit, vertical shading representing under pressure, inclined shadingrepresenting closed to atmosphere, and no shading representing open toatmosphere. The upper part of the diagram relates to the call chamberand the lower part to the recall chamber.

As will be seen, and in correspondence with the description alreadygiven, the call chamber is closed very shortly after (it is shown in thediagram as closed at 0) so that no communication to atmosphere exists.Between 30 and l20 pressure from the pressure line exists inside thecall chamber and produces a writing operation by outward movement of theselected type bar. At approximately 150 the call chamber is opened toatmosphere so that the described pressure equalising and returnprocesses can take place. Between about l80 and 330 the recall chamberis closed ofi' from atmosphere and pressure operated return of the typebar to its rest position occurs between about 210 and 300. Between 330and 360 there occurs pressure equalising in preparation of the chambersfor a fresh writing operation, which is repeated when 0 is reached.

FIG. 14 is an overall view of a writing machine in accordance with theinvention and having a writing mechanism as described already. Hereagain the last two figures in the references used in FIG. 14 are chosento identify parts corresponding with parts in the earlier drawings. inaccordance with this method of referencing the platen is referenced 624.As will be seen the type bars 610 with the type characters 612 at theirends are so short that a large number can be fitted in a circulararrangement without the provision of costly mechanical control andactuating elements in the region of their pivot axes. A selector bararrangement 672, provided around the type bars 610 has cut-away portionsarranged in accordance with a predetermined code distribution so thatselection of one type bar 610 for operation requires a mutual rotationof the selector bars by a certain amount in the peripheral direction soas to form a gap for the selected type bar. This displacement orre-locating can be effected by pneumatic, hydraulic or electromagneticdrive devices 675, which are connected with the extensions 677 on theselector bars via coupling members 676.

The pneumatic or hydraulic drive can be seen in the lower part of FIG.14 and may take nay of the forms already described. ln FIG. 14 it isassumed to be assigned to all the type bars 610 in common.

What is claimed is:

l. A writing machine of the kind in which successive writing ofcharacters side by side and line by line is effected on a record carrierby means of a plurality of character carrying type bars arranged side byside of an arcuate pivot axis in their at rest position and adapted,when actuated, to pivot to effect recording at a common recording point,said record carrier mounted on a platen and including means toincrementally move said platen, comprising:

a. a fluid drive,

b. a plurality of fluid driven members, at least one of said fluiddriven members associated with each said type bar and operable whenfluidly connected to said fluid drive to pivot the type bar associatedwith said drive member to said common recording point,

c. a plurality of selector valve means, one of said selector valve meansassociated with each of said fluid driven members,

d. common means fluidly communicating said fluid drive to each of saidselector valve means;

e. first means to selectively actuate said selector valve means toselectively fluidly communicate said fluid drive to the driven member topivot the selected type bar to the common recording point. and

f. second means for fluidly communicating said fluid drive to the drivenmember of the selected type bar to urge the selected type bar toward itsat rest position.

2. A machine as claimed in claim 1,

wherein a drive lever bar is assigned to each drive element and ispositively coupled with the respective type bar, and the selector meansare so arranged that each can be held in a selected position for aperiod of time sufficient to allow negative pressure produced in thedrive to effect return of a previously driven drive element into itsrest position.

3. A machine as claimed in claim I, wherein there is provided at leastone pressure chamber which is concentric with the arcuate pivot axis ofthe type bars and is in constant communication with the drive, thevolume of said chamber being limited by each of a number of selectorslide valves equal to the number of type bars, each of said slide valvesbeing arranged to be released by the selector means to move into aposition in which communication is established between said pressurechamber and an appropriate drive element.

4. A machine as claimed in claim 3 wherein there are two concentricpressure chambers of which one is in constant communication with driveelements which are provided for the type bars and which, if actuated byfluid pressure, return their respective type bars into the restposition.

5. A machine as claimed in claim 4 wherein a double ended drive lever isassigned to each first and second drive element and is positivelycoupled with the respective type bar.

6. The machine as claimed in claim 4 wherein there is provided means forestablishing a connection via the drive between the concentric chamberand atmosphere.

7. A machine as claimed in claim 6 wherein control slide valves coupledwith the drive shaft are provided, said control slide valves beingarranged when in predetermined positions of said drive shaft to open aconnection between the concentric pressure chambers and atmosphere.

8. A machine as claimed in claim 4 wherein connection between theconcentric pressure chambers is provided via the rotary valvearrangement.

9. A machine as claimed in claim 8 wherein the rotary valve arrangementcomprises a sleeve rotatably mounted on a cylindrical rod and aconnection provided between a peripheral groove in the sleeve and thespace between said sleeve and said rod.

10. A machine as claimed in claim 8, wherein the first and secondconcentric pressure chambers are the terminal spaces of a bore, aselector slide valve in the form of a piston rod is arranged inside saidbore, both pressure chambers being in communication with peripheralgrooves in a rotary sleeve forming part of the rotary valve arrangementand the arrangement being such that in the two terminal positions of theselector slide vaive respectively one of the two drive elements has thespace in front of its working surface connected with at mosphere.

11. A machine as claimed in claim 10 wherein the connections toatmosphere run past a portion of the selector slide valve having areduced diameter.

12. A machine as claimed in claim 3 wherein the selector slide valvesare arranged to move each to a rest position to open connections betweenthe respective drive element and atmosphere.

13. A machine as claimed in claim 12 wherein the pressure chamber isconnected with atmosphere via the drive in the extreme negative pressureposition of said drive.

14. A machine as claimed in claim 13 wherein the drive is provided by adiaphragm pump coupled with an eccentric rotary drive, said connectionto atmosphere in the extreme negative pressure position of the drivebeing provided by bores in the eccentric rotary drive and in thediaphragm and a flexible connection between the eccentric rotary driveand the diaphragm.

15. A machine as claimed in claim 12 wherein the respective selectorslide valves are constructed like piston rods and are inside boresconnected with the pressure chamber, each slide valve having a portionof reduced diameter provided between its ends, ports being provided insaid bores proximate the reduced diameter portion of said slide valveand said slide valve which place said ports in communication withrespectively the working space of the respective drive element andatmosphere according to its position.

16. A machine as claimed in claim 3 wherein there is provided means forestablishing a connection via the drive between a concentric chamber andatmosphere.

17. A machine as claimed in claim 16 wherein control slide valvescoupled with the drive shaft are provided, said control slide valvesbeing arranged when in predetermined positions of said drive shaft toopen a connection between the concentric pressure chambers andatmosphere.

18. The invention as defined in claim 1 and in which said fluid drive isa pulsating fluid drive supplying fluid pressure to said selector valvemeans, said fluid pressure cyclically vacillating between a positive andnegative fluid pressure at a frequency equal to an integral multiple ofthe speed of writing.

19. The invention as defined in claim 18 wherein said actuated selectorvalve means is actuated during the period of positive fluid pressure andremains actuated into the period of negative pressure. said negativepressure being operable to initiate the return of said driven member toits original position.

20. The invention as defined in claim 19 wherein said negative pressureis operable to urge said actuated selector valve means toward itsunactuated position.

21. A machine as claimed in claim 18 wherein the fluid drive is providedby means ofa rotating drive shaft driving at least one pumping devicevia an eccentric.

22. A machine as claimed in claim 21 wherein there are two pumpingdevices so coupled with the drive shaft as to work in phase-displacedmanner with reference to one another.

23. A machine as claimed in claim 22 wherein the phase displacement issubstantially 24. The invention as defined in claim 1 wherein the driveelement for moving the type bar to said common recording point is apiston which is arranged inside a bore, and which in a predeterminedworking position opens a connection between said bore and atmosphere.

25. The invention as defined in claim 1, wherein means are provided forcausing the drive force which is applied to move the selected type bartowards its striking position from its rest position to cease beforesaid striking position is reached, said striking position being thenreached due to stored kinetic energy in said selected type bar.

26. The invention as defined in claim 1 wherein the fluid drive is apneumatic drive.

27. A machine as claimed in claim 18 wherein the pulses are derived bymeans of a rotary valve arrangement which is driven by a rotating driveshaft and to which pressure is supplied from a pressure line.

28. A machine as claimed in claim 27 wherein the rotary valvearrangement comprises a guide block having pressure line port and outletport, a rotatable sleeve disposed in said block, said rotatable sleevehaving peripheral grooves arranged to provide fluid connectionintermittently between said pressure line and outlet ports.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO.3,904,013

DATED 1 September 9, 1975 INVENTOR( i Hermann Rummel It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 15, line 20, delete "324" and insert -342.

line 22, delete "324" and "324a" and insert -342-- and --342a--.

Column 17, line 37, delete "466" and insert --446-.

line 46, delete "even" and insert --event-. line 66, delete "447' andinsert 446-. line 67, delete "468" and insert 458--.

Column 18, line 9, delete "arm" and insert --bar--,.

line 11, delete "diameter" and insert -chamber-. line 20, delete "to"and insert -on--. line 21, delete "by" and insert -to--. line 25, delete"464" and insert --454--. line 61, delete "5" and insert -6--.

Signed and Scaled this tenth Day of February 1976 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer (mnmissloner of Patentsand Trademarks

1. A writing machine of the kind in which successive writing ofcharacters side by side and line by line is effected on a record carrierby means of a plurality of character carrying type bars arranged side byside of an arcuate pivot axis in their at rest position and adapted,when actuated, to pivot to effect recording at a common recording point,said record carrier mounted on a platen and including means toincrementally move said platen, comprising: a. a fluid drive, b. aplurality of fluid driven members, at least one of said fluid drivenmembers associated with each said type bar and operable when fluidlyconnected to said fluid drive to pivot the type bar associated with saiddrive member to said common recording point, c. a plurality of selectorvalve means, one of said selector valve means associated with each ofsaid fluid driven members, d. common means fluidly communicating saidfluid drive to each of said selector valve means; e. first means toselectively actuate said selector valve means to selectively fluidlycommunicate said fluid drive to the driven member to pivot the selectedtype bar to the common recording point, and f. second means for fluidlycommunicating said fluid drive to the driven member of the selected typebar to urge the selected type bar toward its at rest position.
 2. Amachine as claimed in claim 1, wherein a drive lever bar is assigned toeach drive element and is positively coupled with the respective typebar, and the selector means are so arranged that each can be held in aselected position for a period of time sufficient to allow negativepressure produced in the drive to effect return of a previously drivendrive element into its rest position.
 3. A machine as claimed in claim1, wherein there is provided at least one pressure chamber which isconcentric with the arcuate pivot axis of the type bars and is inconstant communication with the drive, the volume of said chamber beinglimited by each of a number of selector slide valves equal to the numberof type bars, each of said slide valves being arranged to be released bythe selector means to move into a position in which communication isestablished between said pressure chamber and an appropriate driveelement.
 4. A machine as claimed in claim 3 wherein there are twoconcentric pressure chambers of which one is in constant communicationwith drive elements which are provided for the type bars and which, ifactuated by fluid pressure, return their respective type bars into therest position.
 5. A machine as claimed in claim 4 wherein a double endeddrive lever is assigned to each first and second drive element and ispositively coupled with the respective type bar.
 6. The machine asclaimed in claim 4 wherein there is provided means for establishing aconnection via the drive between the concentric chamber and atmosphere.7. A machine as claimed in claim 6 wherein control slide valves coupledwith the drive shaft are provided, said control slide valves beingarranged when in predetermined positions of said drive shaft to open aconnection between the concentric pressure chambers and atmosphere.
 8. Amachine as claimed in claim 4 wherein connection between the concentricpressure chambers is provided via the rotary valve arrangement.
 9. Amachine as claimed in claim 8 wherein the rotary valve arrangementcomprises a sleeve rotatably mounted on a cylindrical rod and aconnection provided between a peripheral groove in the sleeve and thespace between said sleeve and said rod.
 10. A machine as claimed inclaim 8, wherein the first and second concentric pressure chambers arethe terminal spaces of a bore, a selector slide valve in the form of apiston rod is arranged inside said bore, both pressure chambers being incommunication with peripheral grooves in a rotary sleeve forming part ofthe rotary valve arrangement and the arrangement being sucH that in thetwo terminal positions of the selector slide valve respectively one ofthe two drive elements has the space in front of its working surfaceconnected with atmosphere.
 11. A machine as claimed in claim 10 whereinthe connections to atmosphere run past a portion of the selector slidevalve having a reduced diameter.
 12. A machine as claimed in claim 3wherein the selector slide valves are arranged to move each to a restposition to open connections between the respective drive element andatmosphere.
 13. A machine as claimed in claim 12 wherein the pressurechamber is connected with atmosphere via the drive in the extremenegative pressure position of said drive.
 14. A machine as claimed inclaim 13 wherein the drive is provided by a diaphragm pump coupled withan eccentric rotary drive, said connection to atmosphere in the extremenegative pressure position of the drive being provided by bores in theeccentric rotary drive and in the diaphragm and a flexible connectionbetween the eccentric rotary drive and the diaphragm.
 15. A machine asclaimed in claim 12 wherein the respective selector slide valves areconstructed like piston rods and are inside bores connected with thepressure chamber, each slide valve having a portion of reduced diameterprovided between its ends, ports being provided in said bores proximatethe reduced diameter portion of said slide valve and said slide valvewhich place said ports in communication with respectively the workingspace of the respective drive element and atmosphere according to itsposition.
 16. A machine as claimed in claim 3 wherein there is providedmeans for establishing a connection via the drive between a concentricchamber and atmosphere.
 17. A machine as claimed in claim 16 whereincontrol slide valves coupled with the drive shaft are provided, saidcontrol slide valves being arranged when in predetermined positions ofsaid drive shaft to open a connection between the concentric pressurechambers and atmosphere.
 18. The invention as defined in claim 1 and inwhich said fluid drive is a pulsating fluid drive supplying fluidpressure to said selector valve means, said fluid pressure cyclicallyvacillating between a positive and negative fluid pressure at afrequency equal to an integral multiple of the speed of writing.
 19. Theinvention as defined in claim 18 wherein said actuated selector valvemeans is actuated during the period of positive fluid pressure andremains actuated into the period of negative pressure, said negativepressure being operable to initiate the return of said driven member toits original position.
 20. The invention as defined in claim 19 whereinsaid negative pressure is operable to urge said actuated selector valvemeans toward its unactuated position.
 21. A machine as claimed in claim18 wherein the fluid drive is provided by means of a rotating driveshaft driving at least one pumping device via an eccentric.
 22. Amachine as claimed in claim 21 wherein there are two pumping devices socoupled with the drive shaft as to work in phase-displaced manner withreference to one another.
 23. A machine as claimed in claim 22 whereinthe phase displacement is substantially 180*.
 24. The invention asdefined in claim 1 wherein the drive element for moving the type bar tosaid common recording point is a piston which is arranged inside a bore,and which in a predetermined working position opens a connection betweensaid bore and atmosphere.
 25. The invention as defined in claim 1,wherein means are provided for causing the drive force which is appliedto move the selected type bar towards its striking position from itsrest position to cease before said striking position is reached, saidstriking position being then reached due to stored kinetic energy insaid selected type bar.
 26. The invention as defined in claim 1 whereinthe fluid drive is a pneumatic drive.
 27. A machine as claimed in claim18 wherein the pulses are Derived by means of a rotary valve arrangementwhich is driven by a rotating drive shaft and to which pressure issupplied from a pressure line.
 28. A machine as claimed in claim 27wherein the rotary valve arrangement comprises a guide block havingpressure line port and outlet port, a rotatable sleeve disposed in saidblock, said rotatable sleeve having peripheral grooves arranged toprovide fluid connection intermittently between said pressure line andoutlet ports.